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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS盒子模型演示</title>
    <link rel="stylesheet" href="css_four.css">
</head>
<body>
   <h1>h1-块级盒子</h1>
   <p>p-块级盒子</p>
   <pre>pre-块级盒子</pre>
   <div>div-块级盒子</div>

   <span>span-内联盒子</span>
   <span>span-内联盒子</span>
   <a href="#">a-内联盒子</a>
   <b>b-内联盒子</b>

   <div class="box_before"></div>
   <div class="box"></div>
   <div class="box_after"></div>

   <div class="box_outline">
       <div class="box_size">1<br>1<br>1<br>1<br>1<br></div>
    </div>

   <div class="box_outline">
      <div class="box_margin"></div>
      <div class="box_margin2"></div>
   </div>

   <div class="box_outline">
      <p>1</p>
      <p>2</p>
      <p>3</p>
 </div>

 

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